A generator set typically includes a generator and a prime mover, for example a combustion engine. In a typical generator set, a mixture of fuel and air is burned within the combustion engine and a mechanical rotation is generated that drives the generator to produce electrical power. Ideally, the engine drives the generator and accordingly produces electrical power having relatively constant characteristics (frequency, voltage, etc.).
Generator sets are often used as a source of power, for example, to supply electric machinery, such as an electric shovel, with power. Likewise generator sets may supply a hospital, a manufacturing facility, a military facility, or the like with power. Although effective, the generator set cannot respond immediately to sudden changes in power demand. For example, when an electric shovel starts to operate a motor that is carrying a heavy load, the power demand can quickly increase. As such, without intervention, a change in power demand can result in an abrupt and undesirable frequency change in the output power. On the other hand, if the generator set is implemented with a large prime mover and generator, changes in power demands are not as critical and changes in the frequency are minimal. However, cost, size, and/or weight of the larger generator set increase dramatically and efficiency decreases dramatically.
One attempt to minimize fluctuations in characteristics of the electrical power output provided by a power generation system is described in U.S. Pat. No. 7,839,027 ('027 patent). The '027 patent discloses systems, apparatus, and methods for maintaining the state of charge of energy storage devices such as batteries, flywheels, capacitors, or other technologies that are energetically coupled with the electricity grid to support ancillary services. To reliably respond to requests to regulate the grid, the charge on the energy storage device is sustained or restored to a specified range in a manner that optimizes the readiness of the energy storage device to supply ancillary services in light of the condition of the grid. A state of charge (SOC) of the energy storage device and the grid frequency may be monitored. When a request from the operator to regulate the grid frequency is not being serviced, the charge of the energy storage device may be increased or decreased so that the charge may be sustained within the specific range. Once the SOC falls outside of the first range, charge may be added to or removed from the energy storage device when the grid frequency has appropriate values, e.g. if the grid frequency is respectively above a first setpoint or below a second setpoint.
The '027 patent however does not utilize a discharge process to ensure the frequency error is quickly reduced. Moreover, the '027 patent is directed to power grids and not to generator sets operating in conjunction with smaller systems having greater demand fluctuations.
Accordingly, there is needed a less costly generator set and process that can minimize power fluctuations and prevent frequency variations when a load is applied.